This invention relates to a storage apparatus which has a rotatable recording medium and which is randomly accessible to one of a plurality of signal recording tracks formed on the medium.
More particularly, this invention relates to a storage apparatus which can read out from one of a plurality of tracks recorded on a rotary disk, video signals stored therein.
More specifically, this invention relates to a storage apparatus where, even in a case when a track address information stored in each of a plurality of tracks for random access has been read out and an error has been detected in the track address signal read out, it is possible to detect a predetermined target track and to read out a signal therefrom.
In a prior-art video information file employing a magnetic disk, the track interval is wide (approximately 500 .mu.m), and the high-speed search of any desired address is obtained merely by detecting a mechanical position.
In an optical video disk device wherein video information are played back with a light beam, there is known a technique for searching for a desired one of a plurality of tracks on a disk at high speed as described in Japanese Published Unexamined Patent Application No. 51-21727.
This technique is characterized in that a large number of tracks are recorded on the rotary recording member and that one of the tracks is selected so as to play back video information contained in the particular track. An access system is adopted wherein address signals for selecting the tracks are recorded in the respective tracks in advance, a determination is made as to whether or not the address signal read out from one track in the vicinity of a target address is the predetermined target address and the track of the predetermined target address is determined on the basis of the determination as detection result. Accordingly, unless the address signal read out is correct, a track of an address of a very different value will be mistaken as the target track and played back. Since information are recorded at a very high density in the actual recording, it is often the case that errors of the address signals develop due to transient phenomena, drop-out etc. in reading out the addresses. It is therefore difficult to precisely select any tracks at random.
A technique for coping with such errors of address signals is described in Japanese Published Unexamined Patent Application No. 52-114305. This patent application has been filed claiming the priority based on British Patent Application Ser. No. 11119/76.
In the specification of such application, a technique is described wherein address signals are provided in a plurality of places within each track is advance, the plurality of address signals are read out for determining whether or not a certain track is a predetermined target track, and majority logic is applied to the plurality of address signals read out, so as to select the correct address.
However, if the address signals include errors, it is sometimes the case that the correct address cannot be uniquely determined by the majority logic. Accordingly, even the technique of this application cannot perfectly cope with the errors of the address signals.